1. Field of the Invention
The present invention relates generally to a novel body configuration for an electronic stringed musical instrument. More particularly, the invention relates to an improved body for an electronic stringed instrument adapted to produce the musical sounds of a banjo.
2. Brief Description of the Prior Art
Prior art banjos consist of a drum and a neck. The drum generally includes a rim and a thin, flexible membrane which is tautly stretched over the rim. This tautly stretched diaphragm is commonly referred to as the "head" of the banjo. The neck is attached to and extends from the rim. A tailpiece is mounted to the side of the rim opposite to which the neck is attached. The strings are secured to the tailpiece, extend across the head and along the length of the neck, and are secured at the remote end of the neck by adjustable pegs. An additional string extends along only a portion of the neck and is secured by another adjustable peg. A bridge is placed between the strings and the head membrane to convey the vibration of the strings to the head, thereby achieving the tonal qualities of the banjo.
There have been many attempts to electrify the sounds of a banjo. A significant reason why these attempts have met without success is that banjos have substantially different operating characteristics in comparison with other musical instruments. A primary determinant of the acoustic properties of an instrument like a guitar or violin is the design of the resonating box. When the strings of such an instrument are plucked or strummed, the vibrations of the strings are transmitted to the resonating box, through a bridge. The vibrations that are induced in the box determine the characteristic sounds of the instrument. An electrical pickup element that is intended for use with an instrument of this type is designed to pick up the vibrations within the resonance box. Typically, the pickup element might comprise a piezoelectric crystal that is attached to one of the walls of the resonance box.
A banjo does not have a resonance box to determine its characteristic sounds. Rather, when the strings of the banjo are plucked, the strings induce vibrations in the bridge, which in turn are transmitted to the head to produce the desired sounds. In contrast with a number of other stringed instruments, the bridge of a banjo is not permanently secured to the head. It is merely held against the head by the tension of the strings. Consequently, when the head vibrates in response to the plucking of the strings, there is relative movement and change in tension between the head and the bridge. The bridge effectively "bounces" on the diaphragm. Thus, the elements of a banjo that produce its characteristic sounds interplay differently than those found in other stringed instruments.
Early attempts to electrically reproduce the sounds of a banjo involved placing a standard pickup element in contact with the head to detect its vibrations. One example of a pickup arrangement of this type is disclosed in Law U.S. Pat. No. 3,780,202. This patent discloses a bracket for adjustably positioning an electromagnetic pickup in any of a number of different positions against the back side of the head. Although this arrangement can detect the vibrations of the head, the sound which is ultimately reproduced does not have the same tonal properties as those of a banjo standing alone. The pressure of the pickup element against the head alters the acoustic properties of the instrument. In other words, the head is not free to vibrate as a whole in response to the motion of the bridge. Rather, some of its movement is dampened by the pickup element, which results in the production of a muffled sound. Another problem with this type of arrangement has been that it is sensitive to feedback.
For the very same reason, a number of other approaches in which the pickup is incorporated into the structure of the bridge are not considered to be totally successful when used in connection with a banjo. In one such arrangement a piezoelectric element forms a transverse layer of the bridge. This arrangement can be found in electric guitars, electro-pianos and the like, but it is not desirable for use in an acoustic instrument because it alters the acoustic properties of the instrument. More specifically, by substituting a layer of the piezoelectric material for the wood, plastic or other conventional material of a bridge, a discontinuity is introduced in the bridge and the transmission of the vibrations to the sound box or the banjo head is altered. Usually, this alteration results in a dampening of the acoustic tone of the instrument, rather than merely reporting it; and is therefore not suitable in those situations in which it is desirable to accurately reproduce the sounds of an acoustic musical instrument with electronic amplification. This arrangement is also sensitive to feedback.
Similarly, attempts to reproduce the sounds of a banjo by placing a piezoelectric element in a slot or recess within the bridge have been met without success. One such arrangement can be found in Shubb U.S. Pat. No. 4,450,744. For the very same reasons stated above, these arrangements do not provide the most accurate report of the instrument's sounds and have still been met with substantial feedback.
Another problem associated with acoustic instruments is that the materials used to make the instruments expand and contract with changing temperature, humidity, and pressure. This problem is especially significant in banjos since banjos are generally made of wood, and wood expands and contracts significantly with changing atmospheric conditions. Therefore, players find themselves tuning and re-tuning their instruments repetitively.
FIG. 1 illustrates a prior art banjo body 10 incorporating a pickup 19 on or in a bridge 18 to reproduce the instrument's sounds. The prior art banjo body 10 includes a rim 15 and a thin, flexible diaphragm 16 which is tautly stretched over the rim 15. A neck 14 with fretboard 28 is attached to and extends from the rim 15. A tailpiece 20 is mounted on the opposite side of the rim to which the neck 14 is attached. The strings 22 are secured to the tailpiece 20, extend across the head 16 and along the length of the neck 14, and are secured at the remote end of the neck 14 to a headstock 12. The strings 22 are secured to the headstock 12 by rotatable pegs or screws 13 that provide for individual adjustment of the tension of the strings. An additional string 24 of the banjo extends along only a portion of the neck and is secured by another adjustable peg 26. Each of the strings 22, 24 is spaced from and supported parallel to the head 16 by means of the bridge 18, which is held against the head by the tension of the strings 22, 24.
As each string of the instrument is strummed or plucked, it vibrates at a frequency determined by its size and effective length, i.e. the length of the portion of the string between the bridge 18 and the particular fret 28 on the neck 14 against which a player urges the string. These vibrations are induced in the bridge 18 which in turn transmits them to the head 16. Since the bridge 18 basically rests on the diaphragm 16, as opposed to being permanently affixed to it, the bridge 18 effectively "bounces" on the diaphragm 16 fluctuating the tension at their interface. Because the pickup 19 is incorporated on or in the bridge 18, the head 16 is not free to vibrate as a whole in response to the motion of the bridge. Rather, some of its movement is dampened by the pressure of the pickup element 19, which results in the production of a muffled sound.